Automatic clutch for motor vehicles



Oct. 28, '1941. B. BURNS 2,250,795

' AUTOMATIC CLUTCH FoRMoToR VEHICLES original 4Filed Jem.n 3o, 19.39 ssheets-sheet 1 B. BURNS Oct. 28, 1941.

v AUTOMATIC CLUTCH FORMOIOR'VEHICLES Original Filed Jan. 30, 1939 5Sheets-'Shet 2 Oct. 2s, 1941.

B. BURNS AUToMATIc CLUTCH FoRMoToRivEHIcLES original Filed Jan. so,193'9 3 Sheets-Sheet 3 /26 /az /33 g Z7 9. 2

U /07 /az ifm 770' /Pacf- 5l/RMS.

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Patented oer. 28,1941

AUTOMATIC CLUTCH VEHICLES FOR MOTOR Bruce Burns, Santa Monica, Calif.,assignor to Salsbury Corporation, Inglewood, Calif., a corporation ofCalifornia Original application Januaryl 30, 1939, SerialNo.

253,55'1. Divided and this application Septembei' 29, 1939, Serial No.91,064

comme.

This invention relates to clutches and more particularly to an automaticclutch' adapted to be'used in light weight motor vehicles and to serveas power transmitting means between the engine and a drivenroad-engaging wheel of the vehicle.

. It is an object of my invention to provide an automatic clutch throughwhich the driven wheel or wheels of a vehicle may be automaticallyconnected and disconnected with the engine at a certain critical speedof the engine withoutI attention from the driver of the vehicle. l

Another object of the invention is to provide, in a motor vehicle,automatic clutch means which permits free idling of the engine withinits normal idling range, but in which the clutch is automaticallyengaged to cause forward movement of the vehicle when the speed of theengine exceeds a predetermined value.

Still another object is to provide an automatic clutch constructionwhichv is cheap to construct.

in large quantities, which is eiilcient and convenient to operate, whichrequires a. minimum of attention, and which is of long life.

. 'I'hese and other apparent objects I attain in a manner which will beclear from a consideration of the following description taken inconnection with the accompanying drawings, in which:

Fig. 1 is a view partly in cross-section oi.' a preferred form of theautomatic clutch appa- `ratus in driving position and an associateddriven pulley forming a part of a vehicle driving mechanism;

Fig. 2 is 'a partial cross-sectional view with the clutch mechanism ofFig. 1 shown in' idling posi- Fig. 3 is a sectional View of the clutchmechanism taken along'the line 0 0 of Fig. 1, looking in the directionindicatedby the arrows; Fig. 4 is a horizontal sectional view of theclutch mechanism taken on the line 4 4 of Fig. 1, looking in .thedirection indicated by the arrows:

Fig. 5 is a sectioned view of the clutch meeha- U nism' taken along .theline 0 5 of Fig. 1 in the direction indicated by the arrows;

Fig. 6 is a partial plan view of the clutch shown in Fig.v 1, looking inthe direction indicated by the arrow 6 Fig. 'I is a sectional view ofthe driven element of the transmission shown in Fig. l taken along 8 0of Fig. 1 in the direction indicated by the arrows;

Figs. 9, 10 and 1l, respectively, are cross-sectional views of portionsof alternative formsv of clutches.

The clutch means constituting the present invention is particularlyuseful for driving light weight vehicles adapted for messenger land/orlight delivery service. The vehicle I(not shown) is propelled by anengine, generally indicated by the numeral 4|, having a crankshaft 44.lAssociated with the crankshaft 44 of the engine 4| is an automaticclutch unit 45 which is in driving relation with a"countershaft unit 46through a V-belt 41. The "countershaft unit 40 is mounted 'on acountershaft 48 rotatably supported inbearfrom a bearing boss |00 on theside of the crankcase |0 of the engine 4| and carries ahub |02 and ahousing |03 which are preferably welded together. A pair ofdiametrically opposed flat faces |04 crankshaft 44 engages mating fiatsurfaces in the end of the hub |02 in such manner that the crankshaft 44,and the hub |02 are rotatively keyed together. A nut |00 engagesthreads on the extended end of the crankshaft 44 and. acting through awasher |06, holds the hub |02 firmly in place on the crankshaft 44.Freely Journaled on the cylindrical outer surface of the hub |02, withsuitable end clearance, is a bushing |01 which is pressed into andcarries a tubular pulley hub |00. An inclined pulley face ||0 is weldedto the exterior of the pulley hub |00.

Another 'inclined pulley face opposed to the pulley face ||0 is adaptedto slide and rotate the line 1 1 in the direction indicated bythearrows;

Fig. 8 is a' sectional view taken on the line on the pulley hub |08and-for this purpose the pulley face is welded on a sleeve |-|2 withinwhich are pressed `a pair of spaced, hardened steel bushings I Il whichslide on the hardened yand ground exterior surface of thepulley hub |00.Three posts ||4 are riveted to the pulley'V face at circumferentlallyspaced locations. and through a hole in each of these posts .a

, spring lil passes and is anchored so as to permit it to oscillate in aplane parallel tothe axis of Athe unit 4I, but to be retained againstthe action milled on the extended end of theber |31.

are riveted to a dish-shaped housing H1. The

' housing ||1 is formed with a series of circumferentially spaced keys||8 which engage corresponding slots |20 in the end of the pulley hub|08 and are held in place by a snap ring |2| engaging a groove on thepulley hub |08. Compression type helical coil springs |22 and |23surroundthe pulley-hub |03 and are compressed between the housing I1 andthe pulley face thus urging the pulley face toward the pulley face atall times. It is apparent that the pulley face is axially movablerelative to the pulley face ||0 and the housing ||1, but is constrainedto rotate therewith byreason of the torque link springs ||5.

Referring now to that portion of the unit 45 posts ||6 which whichfunctions as an automatic clutch, it will be seen that an annular rampis spun in place at |26 to form an integral unit with the housing |03and the hub |02. Shrouded within the ramp member |25 is a floating plate|21 which is free to move axially relative to the ramp but is rotativelykeyed thereto by fingers |28 which pass through holes in the ramp |25.Disposed annularly between the floating plate |21and the ramp |25 is aclrcumferentially resilient centrifugal element, preferably having theform of a grommet spring |30, and preferably consisting of a closely`wound spring with its ends hooked -together to form a ring and withinwhich is a similar spring |3| of smaller pitch diameter with its endsleft free. The grommet spring |30 is preferably so wound andproportioned that when in place within the ramp of the ramp. The ramp`|25 is so shaped that it approaches the plate |21 as it proceedsoutwardly from the axis of rotation, so that enlargement of the grommetspring |30 to a larger radius results in movement of the'grommet springtoward the floating .plate |21. Located between the floating plate |21and the housing |03 is a clutch element preferably comprising an annularmetal plate |32 having friction faces |33 and |34 riveted to oppositesides thereof. The innermost portion of the plate |32 is sheared andformed to produce a series of spaced teeth |35 which mesh with -a matingseries |35 on a member |31 which is permanently at- |25, it retractsitself into I `firm contact with the curved innermost portion ofsimilarly formed teeth.

tached to the concave side of the pulley face ||0 by lugs |39 passingthrough holes in the mem- As seen best in Fig. 4, the teeth |35 areformed by shearing the innermost edge of theplate |32 radially andbending theadjaceni portions away from the line of shear into planesperpendicular to the plane of the plate |32. In this manner a pair ofteeth is formedleaving a space between, and this operation is repeatedaround the edge of the plate to form a series of such pairs of teeth. Asimilar operation is used to form the pairs of teeth |38 on theoutermost edge of the member |31. The teeth on the two mating membersare so spaced that a pair of teeth |38 fits with suitable clearance inthe space left by bendingv out a pair of the teeth |35, al1 of the teethbeing directed in the same as viewed from the right side in Fig. l.

ythe influence of The member |31 is formed along its innermost edge withinclined teeth |38 which are preferably punched out therefrom, as shownin Fig. 4. The inclined teeth |38 preferably have about a 6 lead angleand have engaging surfaces that extend toward the housing |03 as oneprogresses in a direction opposite-to the direction of rotation of theengine crankshaft 44. A cup-shaped member |40 is shrouded within themember |31 `and has formed along its innermost edge a series of inclinedteeth |4| opposed to and adapted to mate with the inclined teeth |38.Within the member |40 is` pressed a cup |42 which carries an annularring |43 of friction material. A waveform or marcel spring |44 of smallwire is so preformed and positioned to bear on the member |40 and themember |31 to force the friction material |43 into contact with thehousing |03. It will be noted that the pressure of the spring |44 alsotends to hold the pulley face ||0 in the extreme rightward position, asshown in Fig. l.

In the operation of the unit 45, that part of the apparatus lyingbetween the housing |03 and the member |31 serves primarily to permitstarting of the engine 4| by simply moving the vehicle forward. Inlightweight two-wheel and three-wheel vehicles of the type to whichtransmissions of the character of that herein disclosed are most readilyapplicable, it is often inconvenient and expensive to provideconventionaly electric starting mechanisms, and it is usuallyinconvenient, if not undesirably expensive, to provide kick starters orhand cranks. The apparatus of my invention thus overcomes the inherentdisadvantages of the above mentioned types of starting through provisionof the overrunning clutch starting 'mechanism described above.

As illustrated in the drawings, the engine 4| is considered to rotate ina clockwise direction It is apparent that forward motion of the vehiclewith the engine stationary, therefore,results in similar clockwiserotation of the pulley face ||0 under the V-belt 41. r)The inclinedteeth |38 are, therefore, moved in a clockwise direction.v Since thefriction material |43 is held against spring |44, the member |40 and theinclined teeth |4| lag behind the inclined teeth |38 and are thusbrought into engagement therewith. Continued forward motion of thevehicle and resultant clockwise rotation of inclined teeth |38 acts byreason of their inclination to the plane of rotation, to urge the member|40 and the v crankshaft causes the engine to start.

After the engine has started, if the pulley face ||0 be movingslowly, asis usually the case, the engine even at idling speed will rotate fasterthan does the pulley assembly, with the result that the inclinedsurfaces of the teeth |4| will be rotated out of engagement' with theinclined surfaces of teeth |38 and the radial ends of teeth |4| willengage the ends of teeth |38. This leaves the force of the marcel spring|44 as the only force tending to maintain the frictional connectionbetween the material |43 'and housing |03. This force is small comparedto that required to transmit the torque necessary to the housing v|03 byaction of the marcel 4therewith willoccur even under full throttle movethe vehicle, so, with the vehicle stationary, the engine is permitted toidle freely, restrained only by the very slight braking effect caused bycontact of the friction face |43 Vwith the housing |03 under the smallaxial force of the marcel spring |44.

Not only does the above described starting mechanism permit starting theengine 'by pushing the vehicle forward, but it also insures against theengine stalling when the centrifugal clutch is disengaged while -thevehicle is still moving forward under its momentum, for under theseconditions the vehicle will drive the engine throng the inclined teeth|38 and |4|.

This mechanism also acts as an overrunning clutch to permit the vehicleto be pushed backward freely without rotating the engine, which is oftenof advantage. in maneuvering in close quarters. When the vehicle ismoved backwardly the inclined teeth |38 will be rotated in acounterclockwise direction as viewed from the right in Fig. 4 and theradial faces of the teeth |38 and |4| will engage, causing the member|40 to be rotated in a counterclockwise direction also. Thefrictional'force between the friction face |43 and the housing |03,being the result of only the axial force of the marcel spring |44, isinsuicient to transmit any considerable amount of torque, so for allpractical purposes `the engine is left free to idle -or remainstationary while the vehicle is moved backward.

Following starting of the engine as described above, the unit 45 isadapted through 'a centrifugal clutch action to automatically connectthe engine to the pulley to drive the vehicle when the speed of theengine exceeds a certain predetermined value. When the crankshaft 44 ofthe engine is rotating, the hub |02, the housing |03, the ramp |25, andthe iioating plate |21 rotate as a unit. When the speed of rotation islow, as in idling of the engine, the parts occupy positions as. shown inFig. 2. The extended annular coil spring |30 is nested within the ramp|25 and rotates with the ramp. In the position shown in Fig. 2, thespring exerts no axial force` on either the floating plate |21 or theramp |25, permitting the plate |32 to remain stationary while the otherclutch elements rotate about it. The spring tension and total weight ofthe grommet spring are so balanced that, inthe normal idling range ofthe engine, it will remain in the retracted position shown in Fig. 2,but upon increase of engine speed appreciably above the idling rangecentrifugal force actingupon' the grommet spring will expand it radiallyto a greater circumferential length.. As the grommet spring movesoutward it is forced in the direction of the oating plate |21 by thefrusto-conical surface of the ramp |25, and moves the floating V plate|21 into contact with-thefriction face |33.

Continued expansion of the grommet spring |35 causes theplate |32 to bemoved until the friction face |34 contacts the housing |03. when theplate |32 will tend to be driven by trictional contact with a movingsurface on either side. The

clutch in the engaged position is shown in Fig. 1. Gentle engagement ofthe clutch, with slippage,

a hill or pulling a torque of the engine. Rotation of the plate |32during engagement of the clutch is, by-reason of the engagement of theteeth |35 and |35, accompanied by rotation of the Amember |31 and thepulley face ||5 connected therewith.

It will be evident that torque is transmitted through the pulley hub08,housing l|1 and torque link springs ||5 to also rotate thepuiley face.I l. As the clutch is engaged, then, the vehicle moves forward and theclutch remains engaged until, due to the closing of the throttle orincrease in resistance to motion of the vehicle,` the engine speed dropsbelow the speed' at which the clutch initially locked in. When the speeddrops belowthis value, theclutch again slips.

If the engine is 'slowed down due to increased resistance to motionofthe vehicle, as in climbing eavy load, the clutch will slip under fullengi e torque, transmitting this torque to the rest of the transmissionand holding the engine speed down to a speed-slightly below the one atwhich locking in of the clutchy normally occurs. If the increase inresistance t`o travel be sulicient to completely stop the vehicle, theclutch will continue to slip under full engine torque, but it will beimpossible to stall .the engine. If, however, the engine speed beintentionally reduced by closing the throttle, the clutch will dlsengageas the engine speed drops back through the engaging range into thenormal idling range and the engine will then idle freely.

The engine speed at which the clutch starts to en- 'gage as well as thatat which it finally locks in for any particular engine torque may bereadily predetermined by proper balance of the weight of the grommetspring |30, the initial tension of the spring, and the shape of the ramp|25. Individual or combined variation of these factors permitspredetermination of engaging and locking-in speeds over an almostunlimited range.

The automatic clutch unit 35 drives the countershaft unit through the v-belt 41, the two units and 45 comprising an automatic transmissionadapted to vary the effective transmission ratio as the vehicle speedchanges, the ratio of engine speed to wheel speed being high forlowspeeds of' the vehicle and'being decreased as the vehicle speedincreases. The countershaft unit 48 is mounted on the countershaft 48which is supported in the bearings 50 retained in the wheel housing- 40,and is restrained against motion along its o'wn axis by a nut |5|lbearing against the sprocket 5| at one en d of the wheel housing and bya snap ring |5| and a shroud |52 cooperating with a groove in thecountershaft at the other endof the wheel housing.` Gn the end of thecountershaft 45 is mounted apulley' .The hub isiitted to thecountershaft 48 and is rotatively connectedv thereto` by a key |51 whichis positioned in a diametric slot in the -countershaft 45 andengagesdiametrically vopthus begins at some predetermined speed abovefurther slippage between the friction faces |33, |34, and the rotatingsurfaces |53, |21 in contact .posed key-ways |55 in the hub |55. A snapring |55 cooperatingwlth a groove in the countershaft 45 restrains thehub |55 from outward axial movement. For the purpose of compensating forbelt wear.. as hereinafter described, a

vwasher |45 is' positioned surrounding vthe shaft 45 and is limited inits rightward travel by l abutment against the end of the key |51. The'gitward travel of the key |51 in turn is deter- 'l ed byv the'adjustnent of ay screw-|55 in threaded engagement with the shaft 48 andbearing against the key |51.

An axially movable inclined pulley face |6| is opposed to the pulleyface |53 so as to cooperate therewith in providing inclined contactsurfaces for the belt 41, and is piloted on the sleeve |56 by the innertubular portion of an annular ramp |62 which is attached to the pulleyface |6| by bending over the end portion |63 thereof. A cylindrical cage|64 is piloted on the countershaft 48 adjacent the snap ring |5| andcomprises a series of circumferentially spaced ngers |65 extendingthrough circumferentially spaced apertures |66 in the pulley face |6|and apertures |61 in the pulley face |53. The inwardly bent ends offingers |65 are projected over a snap ring |68 surrounding thecylindrical housing portion of the pulley face |53, and are clamped, soas to attach the cage |64 'to the pulley face |53, by a closed clampingring |10 which is sprung over and seated in the outwardly turned ends ofngers |65. Between the fingers |65 the interrupted cylindrical edge ofthe cage |64 is bent inwardly with a V-shape at suitable angles toprovide a series of aligned pairs of fulcrum edges |1|. U-shaped shoes|12 of suitable abrasion-resistant metal are slipped over the fulcrumedges |1|. Pivoted about the fulcrum edges |1| are a plurality ofequalizer arms |13, preferably three in number and equally spaced aroundthe cage |64, which are grooved at |14 to provide bearing grooves forthe fulcrum edges, and apertured at |15 to permit a nger |65 of the cageto pass through. The curved outermost ends of these arms engage the backside of the pulley face |6| and are restrained against circumferen tialand axial movement relative to the pulley face by fingers |16 and |11which form a part of the pulley face and which are bent over the sidesoi the equalizer arms |13 to permit free radial movement of the endsofthe arms along the pulley face. Shoes |18 of abrasion-resistant sheetmetal are retained by the lingers |16 and |11 and interposed between theends of the equalizer arms and the back of the pulley face |6| to permitrelative sliding motion of these parts without lubrication.The'innermost ends oi the equalizer arms |13 bear against thefrustoconical end of a member |80 which is slidably mounted on thecountershaft-48. Hardened steel rings |8| are pressed into the member|80 to provide bearing surfaces in contact with the eountershaft. Themember |80 is urged in the direction of the equalizer arms |13 byresilient means, preferably comprising two compression springs |82 and|83 of different pitch diameters positioned in the space surrounding thecylindrical portion of member |80 and within the sleeve |56, and bearingat one end against the member |80 and at the other end against a washer|84 which abuts diametrically opposed adjusting screws |85 and |86threaded through the hub |55. By means of the adjusting screws |85 and|86 the compression of the springs |82 and |83 may be changed.

It is evident that the force of the springs |82 andv |83 acting throughthe member |80 against the inner ends of the equalizer arms |13 keepsthese arms in firm engagement with the fulcrum edges |1| at all timesand results in the outer ends of the arms |13 exerting a force on the.

pulley face |6| tending to move it toward the opposed faee |53. Sinceall three arms |13 are acted vupon equally, force is evenly applied tothe pulley face |6| and the entire pulley face is moved evenly in anaxial direction. The force against the fulcrum edges |1| holds the cage|64, against the shroud |52 and the snap ring |5I, so that the cage isxed in position relative to the pulley face |53. The reaction of thesprings |82 and |83 against the washer |84 and the screws and |86 holdsthe hub |55 rmly in place against .the snap ring |60.

Within the housing portion of the pulley face member |53 is situated anannular ramp |81 which is loosely piloted at its central hole on thesleeve |56 and more snugly piloted at its periphery by the shoulder |83of the pulley face member |53. Between the ramp |81 and the pulley face|53 a marcel spring |90 is compressed so that it has a slight tendencyto move the ramp |81 toward the opposed ramp |82. Confined between theopposed ramps |62 and |81 is a plurality of steel balls |9| which engagethe ramps |62 and |81 on either side. |62 and |81 are so shaped that theaxial separation therebetween diminishes with increasing distance fromthe countershaft 48, and so that they never open far enough apart topermit the balls |9| to pass out oi' connement between the ramps. Thetendency of the springs |82 and |83 is to cause the pulley face |5| toapproach the pulley face |53, thus bringing the ramps |62 and |81 nearertogether and reducing the diameter of the circle of balls ISL The balls|9| are preferably of such diameter and in such number thatl when theunit 46 is not in rotation the balls lie in an annular ring closelyaround the sleeve |56 with each ball lightly pressed against theadjacent balls by the tendency of the two ramps to approach oneanother.` Rotation of the unit 46 causes the balls |3| to y outwardlyagainst the ramps |62 and |81, forcing the ramp |62, and with it thepulley face |6.|, away from the pulley -face |53 to a point where theincreased force of springs |82 and |83 is suicient to balance thecentrifugal force on the balls |9|. When the countershaft 48 isrotating, then, the position of the pulley face |6| relative to pulleyface |53 is determined by the centrifugal force on the balls |9| whichin turn is a measure of the speed of rotation of the countershaft, orthe speed of the vehicle.

The operation of the countershaft unit 46 in cooperation with the clutchand pulley unit 45 and the V-belt 41 as an automatic transmission willnow be considered. If the springs |82 and |83 are substantiallycompressed by inward ad-v justment of the screws |85 and |86. theypreferably exert sufficient force in their extended position 'to urgethe pulley face |6| toward the pulley face |53 with a greater force thanthat with which the pulley face is urged toward the pulley face ||0 bythe springs |22 and |23 when in their compresser?` position. Therefore,when the vehicle is in slow motion and the units 45 and 46 are rotating,the pulley face |6| will be moved to the closest permissible positionrelative to the pulley face |53, being limited by abutment of the innerends of the arms |13 with the cage |64, or by the belt 41 coming to theposition of minimal pitch diameter on the unit 45. 'I'he belt 41 will beforced to near the outer periphery of the pulley faces |53 and |6|,causing it at the same time to move inwardly between the pulley faces||0 and of unit 45 to occupy a position close to vthe pulley hub |08,and forcing the pulley face away from the pulley face v| |0.agalnst theforce of the springs |22 and |23. Under these circumstances thetransmission ls The ramps y 2,260,796 5 in low gear; that is, it is in acondition wherein it provides .the greatest ratio between engine speedand countershaft speed, or between engine speed and wheel speed. ,e V

If the throttle of engine 4| be opened and the vehicle started forwardby engagement of the clutch in the manner previously descrlbed,thevehicle will move forward in this low gear position. As the wheel speedincreases, increase in rotational velocity of the countershaft 48 willsubject the balls |9| to centrifugal force which will cause them to moveoutward against the confining ramps |62 and |81 and move the pulley face6| away from the pulley face |53 against the force of the springs|82/and |83, as previously described. This will permit the belt 41 tomove to a lower pitch diameter on the unit 46, to which position it willbe forced by reason of the belt moving to a larger pitch diameter on theclutch and pulley unit 45 through action of the springs |22 and |23inurging the pulley face toward the pulley face ||0. In this y conditionthe parts may occupy positions as illustrated in Fig. 1, in which theratio of engine speed to wheel speed has been reduced from thatcorresponding to the low gear condition.

Still further increase in wheel speed willresult in further increase incentrifugal force on the balls |9I, with resultant increaseof the axialforce tending to separate the pulley faces of the countershaft unit 46.'I'his permits the belt 41 to be brought to a smaller pitch diameter onthe unit 46 and to a larger pitch diameter on the unit 45, thus stillfurther reducingv the effective transmission ratio. speed becomessufciently great, the pulley face |6| will be displaced to -the positionof greatest permissible separation in which the member |80 abuts thewasher |49 and the belt 41 lies adjacent the fingers |65 on unit 46 andclose to the periphery of pulley faces and of unit 45, the transmissionthen being in the condition providing the smallest permissible ratio ofengine speed to wheel speed, that is, in high gear condition. I

Itis evident that when the vehicle slows down, relative motion ofthe.various parts will occur in the reverse direction and, when thevehicle comes to astandstill, the belt 41 will again be 1 inthe positionof greatest permissible pitch diameter on the countershaft unit and theballs |9| will again be retracted to their smallest pitch circle. Itwill also be apparent that the speed at which the centrifugal force onthe balls |9| flrst overcomes the resultantspring force and producesshifting of the speed ratio of the transmission and the speed at whichthe transmission flnally reaches the high gear" condition may beadjusted by moving the screws |85 and |86 inwardly to increase theinitial load upon the springs |82 and |83, or outwardly to reduce thisinitial tension. 'Ihe transmission may thus be adjusted as desired tovarious road, load, anddrlving conditions, and by proper proportioningof the parts, almost any type of variation of the effective transmissionratio as a function of ,vehicle speed may be obtained.

While the foregoing description of the opera.-

ytion of the transmission explains the manner in which it changes thetransmission ratio in'response to4 vehicle speed, the transmission ispreferably also adapted to` vary the transmission ratio as the enginetorque changes, in such man-v ner as to render the overall performanceof the transmission much more suitable for propulsion When the wheel ofmotor vehicles than if ratio change were determined solely by vehiclespeed. 'I'he variation of transmission ratio with engine torque` isprincipallya result ofthe positions assumed by the belt 41 relative tothe pulleys of the units 45 and 4.6 when torque is'being transmitted.

In the embodiment of my invention illustrated herein, a further controlelement has been introduced in the' construction to accentuate thecreeping tendency of the belt under certain contions of operation and toreduce it under certain otherconditions, thus further improving vehicleperformance. Reference to Figs. 1, 5, and 6 will show that the torquelink springs of the unit 45 are normally installed so that they areunder compression when driving torque, applied to the housing ||1 by thepulley hub |08, is transmitted through the 'posts |6 into the springs 5.It will be clear that when the springs ||5 are angularly disposedrelative to the plane of' rotation of the unit, the compressive force inthe springs ||5 under forward driving torque will have an axialcomponent tending to move the pulley face I in an axial direction.

In Fig. 9 is shown an alternative form of the clutch portion of the unit45 in which the inclined tooth mechanism for starting is eliminated andthe clutch is engaged for starting by the inward movement of the grommetspring, which results when the unit comes to rest. In this form of theunit 45, a ramp 240 is attached to the housing |03 at |26, as in theform of the apparatus previously described, and has substantially thesame shape in its outwardportion as the ramp inthe form vof the unitshown in Fig. l. The inner portion of the ramp 240, however,l preferablyextends inwardly substantially parallel to the plane of rotation nearlyto the member |31. A floating plate 24|, similar in its outer portion tothe floating plate |21 of the previously described unit, is connectedfor rotatlon with the ramp 240by the ears |28 projecting through holesin the ramp 240. 'I'he inner portion of the floating plate 24| is formedinto a frusta-conical shape directed toward the opposing ramp 240. Thegrommet spring is similar to the spring described in connection with theunit of Fig. 1 except that it is made with a fewer number of" turns inthe outer spring to permit it to retract into a circle of smallerdiameter.

With the construction shown in Fig. 9, itis evident that when themechanism comes to rest, as is the case when the engine stops, thegrommet spring |30 will retract inwardly and by engagement with the ramp240 on one side and the A floating plate 24| on the other side, willforce the floating plate 24| leftward, resulting in engagement of thefloating plate 24| with the friction surface |33, and engagement of thefriction surface |34 with the housing |03. In this condition the engine4| is connected through the clutch to the pulley of the unit and if thevehicle is moved forward, the engine will berotated and will start. Whenthe engine starts, the resultant increase in speed will cause thegrommet spring |30 to expand under the influence of centrifugal forceuntil it occupies the position shown in Fig. 9. In this position theclutch is disen- 'gaged and the engine may idle freely. Further'increase in engine speed will result innormal engagement for driving thevehicle in the inanner set forth previously in connection with theapparatus of Fig. 1. Normal engagement and Y disengagement of the clutchunder variations of vehicle speed, load, and throttle opening, will lalltimes.

, engine.

Cil

to retract to such a point that re-engagement of the clutch for startingis established.

While not essential for the functioning of the mechanism, it isdesirable to provide a spring 242 for the purpose lof centralizing thegrommet spring |30 when in the idling position so that it cannot rotateeccentrically or out of balance, and thus prevent possible partial orintermittent and erratic clutch engagement. This spring 242 may take theform of a marcel spring bearing on the ramp 240 and threaded throughvarious of the ears |28. This spring then urges the floating plate 24|rightward in such manner as to always maintain contact between thegrommet spring |30 and the ramp 240 at one side, and the floating plate24| at the other side.

In the alternative form of the unit 45 shown in Fig. 10, a flat floatingplate 245 parallel to the plane of rotation, is employed on one side ofthe grommet spring |30 and a ramp 246 is positioned on the other side ofthe grommet spring and is so shaped as to approach the plate 245 oneither side of an intermediate diameter. A coil spring- 241 bearing atone end on the housing |03 and at thev other end on the floating plate245 assures contact of the grommet spring |30 with both the floatingplate 245 and the ramp 245 at In this form of the unit a single member248 takes the place of the disc |32 and the member |31. being connectedat its outer end with the friction faces |33 and |34, and at its innerend to the pulley face by means of the lugs |39. This constructioneliminates the coupling teeth |35 and |36 of the previously describedconstruction, but is accompanied by the disadvantage that as the member248 moves during engagement and disengagement of the clutch, the pulleyface ||0 is also required to move. To permit the limited movementrequired pulley face, the hub |02 is reduced at 250 to permit movementof the bushing |01 upon it.

The operation of the unit illustrated in Fig. l0 is similar to that ofthe shown in Fig. 9. The parts are shown in the position which theywould take during idling of the When the engine stops, the grommetspring |30 retracts inwardly and the curved inner portion of the ramp246 introduces an increased component of axial engaging force which isexerted against the floating plate 245, and in this manner the clutch isengaged preparatory to restarting the engine by motion of the vehicle ina forward .direction As the engine-speeds up from the idling condition,the grommet spring |30 is thrown outward and the clutch is engaged formoving the vehicle forward as previously described.

In Fig. 11 is illustrated an alternative form of the clutch portion ofthe unit 45 in which two grommetV springs are employed to performseparately the functions of clutch engagement 'for engine starting andclutch engagement for movef ment ofthe vehicle. A ramp 25| is providedof the same general character as the ramp |25 in the unit illustrated inFig. land is attached to the housing |03 in a similar manner. The ramp25| has an arcuate inner portion within which is nested the grommetspring 232. Preferably previously described unit 0f this welded to theinner edge of the ramp 25| is another ramp 253 which approaches thefloating plate 245 as it proceeds inwardly and has an arcuate outerportion within which is adapted to be nested a grommet spring 254.Except for the fact that no retracting spring for the floating plate 245is required, the construction of the remainder of the unit is similar tothat previously described in connection with Fig. 10. The parts of themechanism are shown in the positions which they take when the engine isidling. 'Ihe grommet spring 252 cooperates with the ramp 25| and theoating plate 245 to effect clutch engagement at speeds of the enginegreater than idling speed in the same manner as has previously beendescribed in connection with the apparatusof Fig. l. When the enginestops, the grommet spring 254 retracts inwardly to a smaller diameterand by reason of engagement with the ramp 253'forces the floating plate245 to the left, causing the clutch to engage; whereupon the engine mayagain be started by forward mo- While I have described my clutchapparatus in connection with avthree-wheeled vehicle, it will beunderstood that the same transmission may be employed in the propulsionof a two-wheeled vehicle, which, for example, may be of the general typedisclosed in the patent application of Howard B. Lewis, Bruce Burns,Austin E. Elmore, and Esley F. Salsbury, Serial No. 202,868, now U. S.Patent No. 2,225,914, issued Dec. 24, 1940 or in any other suitable formof vehicle. It will also lbe understood that various variations ormodifications in design or construction of the parts of the apparatus ofmy invention other than those disclosed herein may be made by thoseskilled in the art without departing from the spirit and scope of theappended claims.

It will be seen that my invention involves the use of two clutches oneof which may be called the starting clutch Vwhich operates `by thefriction of the-frictional material |43. The other.

may be termed the running clutch and operates by the friction of thefriction faces |33. 'I'he mechanism is so designed that the inclinedteeth |4| tend to throw the starting clutch into action and cause thestarting clutch to start the motor whenever the vehicle is pushedforward with the motor at rest. As soon as the motor exceeds the speedat which it wouldbe driven by the vehicle the starting clutch releases.

To render the starting clutch effective, it is necessary that therunning clutch be. entirely inoperative whenever the motor is rotatingbelow a definite critical-speed. This is accomplished by the centrifugalmeans in the running clutch which renders this clutch operative onlywhen the motor is rotating above this critical speed. In practice withboth the motor and vehicle at rest the vehicle is given a short pushforward which causes the starting clutch to engage and start the motorwhich immediately accelerates to idling speed which is slower than thecritical speed necessary to cause the running clutch to engage. Duringthis acceleration the starting `clutch disengages as soonas the motorexerts tor then rotates at idling speed without driving the vehicleuntil the operator by opening the throttle accelerates it to thecritical speed when the running clutch is automatically thrown intoengagement.

'I'his application is a division of my application Serial No. 253,557,filed January 30, 1939.

I claim as my invention:

1. In power transmission* apparatus associated with a prime mover,andvashaft rotated by said prime mover, the combination of a member mountedto rotate about the axis of said Ishaft; a i

second member connected for rotation with said shaft and shaped toprovide a ramp'extending toward said rst member as it proceeds outwardlyfrom said axis; a plate positioned between said ramp and said rstmember,` said plate being connected with said second member to rotatetherewith but to permit axial movement relative thereto; and acircumferentially resilient centrifugal element disposed annularlyaround said shaft between said ramp and said plate, said element beingadapted to move'outwardly in response to centrifugal force and byengagement with said ramp to move said plate into clutch engaging`contact with said member, the resilience of said centrifugal elementtending to retract it inwardly in opposition `to centrifugal force.

2. In vpower transmission apparatus associated with a prime mover, and ashaft rotated by said prime mover, the combination of: an yaxiallymovable memberv mounted to rotate about the axis of said shaft; meansconnected for rotation with said shaft and providing a surface on oneside of said 4member for engagement therewith and a ramp on the otherside of said member extending toward said member a's it proceedsoutwardly from said axis; and a circumferentially resilient centrifugalelement disposed annularly around said shaft between said ramp and saidmember, said element being adapted to move outwardly in response tocentrifugal force and by engagement with said ramp to move said memberinto clutch engaging contact with said surface, the resilience of' saidcentrifugal element tending to retract it inwardly in opposition tocentrifugal force.

3. In power transmission apparatus associated with a prime mover and ashaft rotated by said prime mover, the combination of: an axiallymovable member mounted to rotate about the axis oi' said shaft; meansconnected for rotation with said shaft andrproviding a surface on oneside of said member for engagement therewith and a ramp von the otherside of said member extending toward said member as it proceedsoutwardly'from said axis; a plate positioned between said ramp and saidmember, said plate being connected to rotate with said ramp but beingaxially movable relative thereto; a circumferentially resilientcentrifugal element disposed annularly around said shaft between saidramp and said plate, said element being adapted to move outwardly inresponse to centrifugal force and by engagement with said ramp to movesaid plate into engagement with said member,

and said member into engagement with said surface, the resilience ofsaid centrifugal element tending to retract it inwardly in opposition tocentrifugal force; and means limiting the inward travel of saidcentrifugal element.

4. In power transmission apparatus associated with a prime mover and ashaft rotated by said prime mover, the combination of movable membermounted to rotate about the axis of said shaft; means connected forrota-tion with said shaft and providing a surface on one side of saidmember for engagement therewith and a ramp on the other side of saidmember extending toward said member as it proceeds outwardly fromsaidaxis; a plate positioned between said ramp and 'said member, saidplate being connected to rotate with said ramp but being axially movablerelative thereto; a continuous coil spring disposedannularly in tensionaround said shaft between'` said ramp and said plate, said spring being'a `apted to move outwardly in response to centrifug` with said ramp tomove said plate into engagement with said member, and said member intoengagement with said surface; and ymeans limit-'1 ing the inward travelof said spring.

5. In power transmission apparatus associated with a prime mover and ashaft rotated by said prime mover, the combination of: an axiallymovable member mounted to. rotate .about the axis of said shaft;'meansconnected for rotation with said shaft and providinga surface on oneside of said member for -engagement therewith -and a ramp on the lotherside of said member .extending toward said member as it proceedsoutwardly from said axis; a plate positioned between said ramp and saidmember, said plate being connected to rotate with said ramp and beingaxially movable relative thereto; an extended annular coil springdisposed between said ramp and said plate, said spring being adapted tomove outwardly in response to centrifugal force and by engagement withsaid ramp to move said plate into engagement with said member, and saidmember into engagement with said surface; a filler. element disposedannularly within said spring, providing increased mass thereto; andmeans limiting the inward travel of said spring. v i

6. In power transmission apparatus associated with a prime mover and ashaft rotated by said prime mover, the combination of an axially movablemember mounted to rotate about the axis of said shaft; means connectedfor rotation with said shaft and providing a surface-on one side of saidmember for engagement therewith and a ramp on the other side ofsaidmember: a plate positioned between said ramp and said ,memben said platebeing connected to rotate with said ramp and being axially movablerelative thereto, said ramp and said plate being-so shaped that theaxial separation therebetween is greatest at a certainvradius, anddecreases with an. axially y force and by engagement v

